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Another PizzaBox

Started by Swapnil, June 20, 2011, 09:53:47 PM

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Swapnil

This one's a total copy-paste of Vaibhav's plane with respect to dimensions.
http://www.rcindia.org/self-designed-diy-and-college-projects/first-flight/

Only differences are:
1) It's made of 4 mm coro + high density thermo,
2) Wing is flat-bottom aerofoil instead of flat,
3) It has a 160 W motor + 9*4.7 prop instead of a 120 W + 8*6 (in Vaibhav's setup).

This bird is certainly heavier than Vaibhav's but i hope the power setup will compensate for that.
Couldn't maiden it as it was raining/ windy all day, will try in the morning.

Questions:

1) The aerofoil has 1 in thickness at 1/3 chord. Will it make any significant difference as compared with flat-wing? (I've read in a post by Sai sir that aerofoils don't give much advantage over flat-wings for small models)

2)The servos are placed close to the elevons. How much will the position of CM have to be changed?

Many thanks to naatumach (Vaibhav Sharma) for the detailed plan.  :thumbsup:
Hope mine flies as well!  :)

naatumach

1.I have also read that airfoils dont make much difference in models.
But that is not entirely true. Try building one fuselage and two sets of identical wings, one with airfoil and one without. The airfoil makes the glide longer and sturdier.
And I believe that especially in my model which i has a less than one thrust to weight ratio, i feel that airfoil makes a difference.
2. Where ever you place the servos, just find the CG of the aircraft and place the 1/3rd line about an inch behind the CG. If the a/c nosedives reduce the distance, if it flares up increase the distance.

The closer you keep the Servo and the battery the better it will fly. The reason is that
There are three heavy components, 1.Motor 2.Battery 3.Servo.
Motor's is fixed. Battery is near the 1/3rd line, so its fixed too. So now you are left with the servos and the plane is balance. Now if the servos are of 10gm and is 1cm from 1/3rd line the torque induced is 10gm.cm and if its 10gm and placed 10cm away it'll cause a torque of 100gm.cm which will cause too much instability, so i recommend the servos be kept close to the 1/3line.

Regards
Motto: build, fly, and modify.
Prefers working on designs than electronics.
No pre-made plans. Use blueprints, make calculations, build, fly, troubleshoot, fly again.

rajathv8

Wow that is one wierd looking plane. UFO :) Post vids too. Plan on giving it colour for visibility? since its more of a square.

naatumach

It is actually a very common design.
If you taper the planform it will resemble a mirage, but its planform is designed for high speed.
To make it adapted for our purpose we make the have a low aspect ratio and viola you get the pizza box.
Motto: build, fly, and modify.
Prefers working on designs than electronics.
No pre-made plans. Use blueprints, make calculations, build, fly, troubleshoot, fly again.

naatumach

Quote from: Swapnil on June 20, 2011, 09:53:47 PM
It has a 160 W motor + 9*4.7 prop instead of a 120 W + 8*6 (in Vaibhav's setup).
How does one find out the Wattage of the motor?
Motto: build, fly, and modify.
Prefers working on designs than electronics.
No pre-made plans. Use blueprints, make calculations, build, fly, troubleshoot, fly again.

Swapnil

Well, it's generally specified in the motor manual.
Also, Wattage = (max. voltage) x (max. current) .....

Swapnil

Quote from: rajathv8 on June 20, 2011, 10:55:13 PM
... Plan on giving it colour for visibility? since its more of a square.

Yup. How about all black? Or maybe black+silver?
It'd look more like a UFO then. ;)

Could also try adding a tractor-beam to kidnap pizzas! ;D

naatumach

So my max voltage is 11.1V (3cell) and max current is 18A (ESC) ? so that makes it 199.8W?
Is this correct?
Motto: build, fly, and modify.
Prefers working on designs than electronics.
No pre-made plans. Use blueprints, make calculations, build, fly, troubleshoot, fly again.

Swapnil

Oh no, you got it wrong!
It's the max. current of the motor you need to consider not that of the ESC (as we are calculating the motor's wattage).

Swapnil

Did some test throws. I don't know if one can use the term 'glide' for a plane with such dimensions, but it did go straight without dipping forward or backward.   

naatumach

I think you're good to go. Yes one really cant use the term glide for it :P
Motto: build, fly, and modify.
Prefers working on designs than electronics.
No pre-made plans. Use blueprints, make calculations, build, fly, troubleshoot, fly again.

Swapnil

The rain gods hate me!  :(

All I could do with it indoors was paint and name it.
Now it's called 'The BugHunter' ! 8)

Pics follow...

Swapnil

Top view...

Swapnil

Upside down..

Swapnil

some more...

Swapnil

and this...

naatumach

is that paint or printed paper or textured paper?
Motto: build, fly, and modify.
Prefers working on designs than electronics.
No pre-made plans. Use blueprints, make calculations, build, fly, troubleshoot, fly again.

Swapnil

Poster colours+paint+varnish+permanent markers...
I assure you, no 'printed paper or textured paper' was harmed during the paint job.  ;) :P ;D

I know it looks like a 6-year-old's work, but that's all I can do with colours! ;) :)

Swapnil

Quote from: rajathv8 on June 20, 2011, 10:55:13 PM
Wow that is one wierd looking plane. UFO :) ...

Well, I initially thought of naming it 'The Pizza-kidnapper from Pluto' or 'The JungleBoy'...but now it's 'The BugHunter'. :D

naatumach

it looks good. shouldn't u hv flown it before you try to decorate it?
im getting too anxious to see it fly
Motto: build, fly, and modify.
Prefers working on designs than electronics.
No pre-made plans. Use blueprints, make calculations, build, fly, troubleshoot, fly again.

Swapnil

Quote from: Swapnil on June 23, 2011, 10:20:51 AM
The rain gods hate me!  :(
All I could do with it indoors was paint and name it.

Rains man!
I 'decorated' it so that even if it doesn't fly, it'll make my wall look impressive! :)

naatumach

Motto: build, fly, and modify.
Prefers working on designs than electronics.
No pre-made plans. Use blueprints, make calculations, build, fly, troubleshoot, fly again.

Swapnil

Increased vertical stabilizer area as suggested by Vivek (Jatayu)....

Swapnil

Took it out this morning.
Broke my first prop! :D :D :D

Swapnil

WooHooooooo!
My BugHunter FLIES! ;D ;D ;D

Just did the maiden.
1) Went straght up at 30o
2) then 3 rolls
3) 1 loop
4) then hovered for like 3s
5) then a bad landing (bent prop adaptor base)

It was Super-Awesome!   ;D ;D ;D
(Anwar sir, can't we get a dancing smiley?  ;D)

A million thanks to Vaibhav (naatumach) and Vivek (Jatayu) for all their technical and non-technical help and for supporting me throughout. Really grateful to you guys!  :) :hatsoff: :bow: {:)}

And sorry guys, no video. Will do another sortie this afternoon on a paddy farm and record it.

PS: This was with a 10*5 prop and launched at 50 % throttle.